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Charging the Battery in the iRobot Roomba
Very often, surfing the Internet, I find people asking questions about why the Roomba (aka Rumba) vacuum cleaner behaves strangely with a good battery. In order to understand where the legs grow from frequently occurring problems, let's try at an amateur level to figure out how the battery charges inside the vacuum cleaner.
Suppose you have inserted a new (or old) battery into your vacuum cleaner and connected a charger to it (to the vacuum cleaner). The first thing a vacuum cleaner does is check its systems (we're not interested in that). Next, he see what is the voltage of the inserted battery. If the voltage is higher than 12 * volts, then standard, fast charging begins. If the battery voltage is below 12 volts *, Roomba will begin a trickle charge for 18 * hours.
If the battery is too discharged (voltage <12V), it means that it was stored in a discharged state for a long time or something else unpleasant happened to it. Therefore, a long charge with a low current should lead to the restoration of "ailing" battery cells. It is very important that you do not interrupt the 18-hour * charge. After all, if you disconnect the rumba from charging for a second, then reconnecting it will start the charging cycle again, that is, checking all systems, then measuring the voltage on the battery ... lasted only a few minutes, it doesn't matter, in the first minutes the charge goes with a significant increase in the voltage on the battery) and Rumba will begin a standard charge cycle. That is, a large current (about 1250mA).
Advice: if you put the rumba on the charging base and see from the indicator that the 18 *-hour charging process has started (the charge indicator blinks very often), then you can try to immediately remove the rumba from the charge and connect the charger plug to the rumba directly. This is done so that someone does not accidentally "kick" the rumba with his foot and interrupt the "life-giving" exercise.
If everything is in order and the initial voltage is normal, then the charge with a large current will go according to the -dV algorithm.
The principle of operation of the -dV - algorithm can be simplified as follows: It is known that after installing an empty battery for charging, at first, the voltage rises very quickly. Then the growth slows down and most of the process, the voltage on the battery rises evenly slowly. But closer to the end of the charge (that is, closer to the saturation of the battery), the voltage begins to grow much faster, then the growth slows down, stops completely and the voltage begins to fall. This peak "acceleration of voltage growth-stabilization-decrease" is what the algorithm catches. But the fact is that also at this very moment, the charging efficiency is rapidly falling and the energy that was previously used to charge the battery now begins to simply turn into heat and the batteries are rapidly heating up. Then -dV - the algorithm completely stops the supply of charging current to the battery, allows it to cool down to 34 * degrees (or a maximum of 2 hours), then the charger turns on again, but in the TRICKLE CHARGE mode - that is, "drip charge" when the charge is supplied with an extremely low current. So small that it does not heat up the batteries excessively. The batteries cool down, the voltage on them drops and it turns out that the battery is far from 100% charged. Firstly, due to the fact that the temperature has dropped. Secondly, due to the fact that some battery cells might not have time to fully charge ... And this drip charge allows you to slowly top up the battery charge to 100%. If we assume that, following the results of a quick charge, the 3.3Ah battery is 70% charged, then it is easy to calculate that 70% of the 3300mAh is 2310mAh. Then the remaining 990mAh will be "refilled" for more than 20 hours !!!! After all, the trickle charge runs with a current of only 50mAh and its efficiency is much less than 100%.
That is why it is believed that rumba should never be removed from the charge. After all, when the charging indicator turns green, it means that only the fast charge mode is stopped, but then, after cooling down, the charge will continue in the Trickle-charge mode (trickle charge). And even when the batteries are 100% charged (and this can happen even after three days), it is still not worth removing Rumba from the charge for two reasons:
Rumba, even when turned off, is quite power hungry for batteries. After all, many write that a charged Rumba, left overnight without charging, may be discharged by morning. This is exaggerated, but not far from the truth.
Even if Rumba did not use the battery charge, the battery itself has a self-discharge. That is, it itself is very slow, but discharges.
And so, in order to compensate for these 2 reasons, let's remember: the rumba should always be on charge. If you leave the house and, for fire safety reasons, want to disconnect the charger, then it is advisable to remove the battery from the rumba for the first reason described above.
Now let's talk about the fact that Rumba "gets used" to the battery. That is, it accumulates information about how much it was charged, how much it was charged, possibly stores information about the temperature of the battery ... This information is hidden behind the wilds of secrecy, but one can speculate.
Let's go back to the beginning of the article and remember that we inserted a new battery into Rumba. Or old. Let's dump in Rumba information about how much and how this battery she charged and discharged. To do this, in the 400 series, you need to remove the battery, press and hold the POWER button for more than 5 seconds, release and then insert the battery. All history of past charges will be deleted. We put the rumba on charge for the 3rd day. Information about 3 days was taken from the forums. Official information says "leave it overnight".According to my personal observations, "at night" may not be enough. I recommend charging a full 24 hours. This will give us 100% charge in 99% of cases. Then the Runet tells us that we need to remove the auto-charging station from the room (so that the vacuum cleaner itself does not come to charge) and turn on the rumba to work with the MAX button (that is, vacuum until the battery is completely depleted). If there is no MAX button, but there is a DOCK button, then press it. Rumba will search in vain for the charging station (which we sadists have previously removed) until the charge is completely depleted. At the same time it vacuums. If there is no DOCK button, then just turn on the vacuum cleaner over and over again until it says that the battery is completely discharged. Vacuum as many rooms as possible at a time.
After the battery has run out completely, reconnect the charging plug to the bearing and charge it again for at least 24 hours. Having done this procedure several times, you will accustom Rumba to this battery. She will know how much charge to expect from him. When, during operation, turn on the yellow indicator, and when the red one. By the way. The first time I gave Rumba my homemade battery after the reset, she was vacuuming with a green indicator until it turned off. That is, the green glowed, glowed and bam ... blinked red to the sad four-note melody. That's it, the battery is dead, and Rumba did not expect this. After the second cycle, it was the other way around: Rumba, turned on immediately after a 24 hour charge cycle, showed a yellow indicator. And only after the third or fifth cycle did the indicator work as it should. First green, then yellowish, yellow, orange, red (when the rumba is still vacuuming and in between times looking for a charging station) and only then blinking red (when the rumba does not move).
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- how to properly charge the battery
Well
DIY Battery for Rumba with your own hands
I scoured the internet for a long time looking for a recipe for making a rumba battery.
Usually it is easier for people: they have an old, dead battery and they only need to replace separately only the dead or even all the cells. And you do not need to bother with fixing the batteries in the rumba ... to find a thermistor ...
It was more difficult for me. I ordered my iRobot Roomba in a used form and without a battery at all. And I didn't want to order a new battery until I checked the performance of the vacuum cleaner itself ... And you can't check a vacuum cleaner without a battery. Well, you get the idea.
Therefore, in a local wholesaler, I bought 12 AA batteries for 2100mAh. And he took not simple NiMh, but the so-called. AlwaysReady: low self-discharge batteries. They say that they have less drawdown under load, more ability to hold a high charge current, longer service life ... etc.
There were also 2300mAh options, but they were significantly (and disproportionately) more expensive. And also there are rumors that more capacious batteries have a higher voltage drop under heavy load.
Further, in the Engels store of radio components, 2 special boxes of Russian production were bought for 15 rubles. I don't know what they are called. Each box allows you to insert 6 AA batteries / accumulators into it and get 7.2V in the case of batteries or 9V in the case of batteries at the output of their boxes.
T. about. 2 boxes of 7.2V gave just the 14.4V we needed (well, yes ... in the original battery there are also 12 cells of 1.2V).
I’ll quickly go over the fact that I "threw out" these boxes due to their incompetence and a friend brought me from Saratov of better quality, Chinese for 25 rubles.
Having soldered the boxes sequentially, I soldered them with wires to the connector of the rumba itself, and fixed them in the battery compartment "in the spacer" by inserting several pieces of cardboard wrapped with electrical tape.
All right. The batteries, when charged in an external charger, pushed the rumba perfectly. But they categorically refused to charge in it. Rather, Roomba itself refused to "feed" them. Although I tried to connect the charger connector to the rumba. Although I "parked" it at the auto-charging station ... The "DOCKED" light came on on the auto-charge, and the charging lamp on the rumba did not blink.Then, in the same radio parts store, a 10kΩ thermistor was bought and soldered between the negative contact and the contact of the rumba temperature sensor. Charging is on! I don’t know: maybe because the thermal sensor is "not native" and its characteristics are slightly different from the required ones, or maybe because the finger batteries are much smaller than the native ones, but at first, when charging, they warmed up to about 70 degrees Celsius. Then (maybe because the rumba got used to them?) The maximum temperature became about 60g, which is already tolerable and does not smell so much of burned electrical tape.
If we take not 12, but 24 batteries, and put them 12 in parallel, then the load on them will drop 2 times, and the temperature should drop significantly, but now I can not find exactly the same batteries anywhere in Engels / Saratov to double the capacity of my battery. Now, having paid about 1000 rubles for a homemade rechargeable battery, I have a capacity of 2100mAh and about 45 minutes of work on velvety linoleum or about 30 minutes of work on a carpet. If you double the number of batteries, then I hope that the runtime can even triple, since the load on the cells will be less and the drawdown under load will also decrease. So the continuation (and addition of photos) follows.
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- the battery can be made by hand
There are also articles about the very device of our battery, but the main thing in them is to let the vacuum cleaner work until it is completely discharged, otherwise the battery will quickly fail.
